| 904L super austenitic stainless steel exhibits good corrosion resistance in acidic environments such as sulfuric acid,hydrochloric acid and nitric acid,but 904 L stainless steel has poor corrosion resistance in hydrofluoric acid solution.The mechanism of the effect of F~-on the passivation film of 904 L stainless steel is not yet clear.Therefore,this paper takes 904 L stainless steel as the research object,using electrochemical methods,XPS,SEM,ICP-OES,etc.The evolution of the passivation film of 904 L stainless steel in F~-and Cl~-containing acidic solutions was studied in depth.At the same time,based on the preliminary research of the research group,the surface strengthening processing of 904 L stainless steel was selected by ultrasonic rolling and magnetron sputtering to discuss its effect on the corrosion resistance of 904 L stainless steel.The research results are as follows:(1)In the F~--containing acid solution,the F~-erosion ability is strong,destroying the integrity of the passivation film,and the probability of forming pitting corrosion is large.By constructing a model of the action mechanism of F~-on the 904 L passivation film,it is revealed that F~-participates in the process of the formation and destruction of the passivation film,that is,the presence of F element in the passivation film constituent elements,and the content of other beneficial elements on the passivation film Reduce,reduce the corrosion resistance of 904 L stainless steel passivation film,the mechanism of F~-on the passivation film is completely different from Cl~-.(2)After 904 L is processed by ultrasonic rolling,the surface roughness is significantly improved,which makes the passivation film formation time fast and the passivation interval range wide.At the same time,it improves the surface integrity of 904 L stainless steel and reduces the pitting nucleation point.The surface hardness is increased,and there are beneficial residual compressive stresses,so that its corrosion resistance is improved.(3)Magnetron sputtering nano-scale grains on the 904 L stainless steel substrate greatly increases the nucleation point of the passivation film,and the passivation film formation speed is fast.This layer of coating significantly improves the corrosion resistance of 904 L stainless steel.The immersion experiment showed that the 904 L stainless steel treated by magnetron sputtering process showed obvious pitting corrosion behavior,while the untreated 904 L not only showed pitting corrosion behavior,but also occurre intergranular corrosion at the grain boundary. |
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